Which logos? You've asked for help with logos in the updated thread title, but you haven't really shown any examples or given much information beyond that.
In any event, it's fairly simple.
1. Get an image of the logo you want to use.
2. Open it in Photoshop or GIMP.
3. Copy the entire image, and create a new image with the same dimensions, and a transparent background.
4. Past the logo image in the new image window.
5. Using the Magic Wand tool, select the areas you want to make transparent, and press the Delete key.
6. Save the file when you're done. You now have a copy of the logo on a transparent background.
Here's a visual guide I found on YouTube. For general image manipulation, you might want to search out some tutorials like this.
For more specific information on creating logo updates for NBA Live 2005 through NBA Live 08, there's this guide:
http://www.nba-live.com/nbalivewiki/ind ... n_Tutorial